Magnification of the amplitude of magnetostrictive radial vibrations



June 1964 L. BALAMUTH ETAL 3,139,543

MAGNIFICATION OF THE AMPLITUDE OF MAGNETOSTRICTIVE RADIAL VIBRATIONS Filed April 25, 1962 INVENTORS LEWIS BALAMUTH 8- ARTHUR KURIS ATTORNEY United States Patent MAGNIFICATION OF THE AMPLITUDE (BF 'MAGNETOSTRICTIVE RADIAL VIBRATIONS Lewis Balamuth, New York, and Arthur Kuris, Bronx,

N.Y., assignors to Cavitron Ultrasonics Inc, Long Island City, N.Y., a corporation of New York Filed Apr. 25, 1962, Ser. No. 190,044 Claims. (Cl. 310-26) This invention relates generally to high frequency acoustic or ultrasonic transducers, and more particularly is directed to improvements in transducers adapted to generate high frequency acoustic or ultrasonic vibrations in radial directions.

Acoustic impedance transformers have been provided, for example, in United States Letters Patent No. Re. 25,- 033, issued August 29, 1961, to Lewis Balamuth and Arthur Kuris, for magnifying the amplitude of high frequency acoustic or ultrasonic vibrations transmitted longitudinally therethrough from a magnetrostrictive or other transducer generating the vibrations to a tool or other utilizer of the vibrational energy. The acoustic impedance transformers of the type disclosed in the previously identified patent are generally formed of a single piece of vibration transmitting material having a longitudinal length substantially corresponding to one-half wavelength of sound traveling longitudinally through the material of the transformer at the frequency of the vibrations which are to be magnified, and the transformer is composed of two parts having substantially different cross-sectional areas which are substantially uniform throughout the major lengths thereof, with the juncture between the two parts being constituted by a portion of variable crosssection confined within a small proportion, for example, 20%, of the total length of the transformer, and with the nodal plane of longitudinal vibration of the transformer being the division between an input section and an output section of substantially different mass so that the transformer is operative to modify the amplitude of longitudinal vibrations transmitted therethrough by virtue, at least in part, of a mass effect.

In a particular acoustic impedance transformer constructed in accordance with the above requirements for modifying the amplitude of vibrations transmitted longi tudinally therethrough, the input and output sections of substantially different mass may be defined by cylindrical portions having suitably different diameters, or by prismatic portions having different cross-sectional dimensions.

When it is desired to provide a connecting body having longitudinally directed vibrations introduced at one end thereof with an output at which radially directed vibrations are achieved, the longitudinally vibrating connecting body may have a disc or ring secured thereon at a nodal plane of its longitudinal vibrations, and the diameter of such disc or ring is selected so that the latter will resonate with the frequency of the longitudinal vibrations in the connecting body. Thus, radial vibrations will be achieved at the periphery of the disc or ring at the frequency of the longitudinal vibrations transmitted to the connecting body from a magnetrostrictive transducer or the like. However, difiiculties are experienced in effecting the magnification of the radial stroke of the vibrations at the periphery of the disc or ring. Merely stepping the thickness of the disc or ring from the center outwardly, as would be suggested by the measures adopted for magnifying the amplitude of longitudinally directed vibrations, as described above, cannot effect magnification of the radially directed vibrations, particularly for the fundamental mode of radial vibration, in which case, all particles at the periphery of the disc or ring move outwardly or inwardly simultaneously so as to satisfy the principle of the conservation of momentum, as is necessary. Since the momentum vectors are radially directed in the case of radial vibrations, any -momentum vector directed outwardly along a given radius from the center of the disc or ring is opposed by a diametrically opposite momentum vector of the same magnitude, and the effect of such opposing momentum vectors is to cancel out any magnification of the amplitude of the radial vibrations that might otherwise be expected to result from the radially outward stepping of the thickness of the disc or ring.

Accordingly, it is the primary object of the present invention to provide structures by which the amplitude of radially directed vibrations may be amplified, thereby to permit the efiicient utilization of such radial vibrations in grinding, honing machining or other operations.

The magnification of radially directed vibrations in accordance with the present invention is generally achieved by providing a radially vibrated disc or ring shaped body with radially directed slots which separate the body into a series of sectors which are arranged so that diametrically opposed sectors have different masses. Since the center of the disc or ring-shaped body constitutes a nodal point of the radial vibrations, the difference between the masses of the two diametrically opposed sectors results in magnification of the radially directed vibrations at the peripheral edge or surface of the sector having the smaller mass.

In order to avoid undesirable gross vibrationsof the radially vibrated body, or of the shaft or axle on which the same may be mounted, the disc or ring-shaped body has the radial slots arranged therein so that sectors of relatively large and small masses alternate around the body, with the large masses being of equal mass and equally angularly spaced and the small masses being of equal mass and also equally angularly spaced, in which case the net center of gravity of the entire body still remains at the geometric center thereof and such body can be rotated, even at relatively high speeds, without dynamic unbalance about its central axis.

In devices embodying this invention, the body which is radially slotted, as indicated above, may form part of the magnetostrictive transducer itself which is further provided with energizing coils extending around portions of the slotted body and supplied wih biased, high frequency alternating current so as to generate radial vibrations directly within the body. Alternatively, in other embodiments of the invention, the radially slotted body may be suitably mounted on a shaft or other connecting body transmitting longitudinal vibrations from a magnetostrictive or other transducer connected to one end thereof so that, when the radially slotted disc or ring-shaped body is located at a nodal plane of the longitudinal vibrations, radial vibrations are set up in the radially slotted body at the frequency of the longitudinal vibrations.

The above, and other objects, features and advantages of the invention, will be apparent in the following detailed description of illustrative embodiments thereof which is to be read in connection with the accompanying drawing, forming a part hereof, and wherein:

FIG. 1 is an elevational view, partly broken away and shown in axial section, of a device embodying the present invention for producing magnified radial vibrations;

FIG. 2 is a transverse sectional view taken along the line 2.--2 on FIG. 1;

FIG. 3 is an axial sectional view of a device for magnifying the amplitude of radially directed vibrations in accordance with another embodiment of the invention;

and

FIG. 4 is a transverse sectional view taken along the line 44 on FIG. 3.

Referring to the drawing in detail, and initially to FIGS. 1 and 2 thereof, it will be seen that a device for producing large amplitude radiallydirected vibrations in accordance with the present invention, and there generally identified by the reference numeral It includes a body 11 of circular configuration which may be brazed, soldered or otherwise secured on a supporting shaft 12. In order to permit rotation of the body ll, shaft 12 may be supported, at its ends as shown, in bearings 13 of a suitable frame 14-.

In the case where the device It) is in the form of a magnetostrictive transducer, as illustrated in FIGS. 1 and 2, the body 11 thereof is formed of magnetostrictive material, such as, nickel, Permanickel, Permendur, or other metals which have high tensile strength and are highly magnetostrictive in character, so that the body 11 will vibrate radially to a maximum degree when subjected to the influence of an alternating electromagnetic field es tablished by the supplying of biased alternating current to windings 15 provided directly on the body II, as hereinafter described in detail.

As is apparent in FIG. 1, the body 11 is preferably formed of an axial series of generally circular laminations 16 which may be stamped or otherwise fabricated from the selected magnetostrictive metal. In accordance with the present invention, the body Ill, and hence each of the laminations 16 making up such body, is formed with generally radially extending slots, as at 17 on FIG. 2, so as to divide each lamination 16 into a circular series of sector-shaped portions 18 and 19.

As is apparent in FIG. 2, the radial slots or cutouts 1'7 are dimensioned and disposed so that the sectors or portions 18 and 19 which are arranged alternately around the lamination have relatively small and relatively large masses, respectively. Further, the lamination 1e has an odd number of each of the different sectors or portions 18 and 19, for example, five sectors 18 of relatively small mass and live sectors 19 of relatively large mass, as in the illustrated embodiment, so that each sector 18 of relatively small mass is diametrically opposed by a sector 19 of relatively large mass.

In the device of FIGS. 1 and 2, the energizing Windings are wound around the relatively narrow stems of the sectors 18 of small mass of a group or stack of the laminations 16 which are axially superposed, so that the high frequency alternating electromagnetic field established by the passage of a biased, suitable high frequency alternating current through the windings 15 induces or generates radially directed vibrations in the sectors 18 at the fundamental mode of radial vibration of the body 11.

Since the diametrically opposed sectors or portions 18 and 19 of each lamination 16 have different masses, balancing of the momenta requires that the average radial velocity in the sector 18 of relatively small mass will be greater than the average radial velocity in the diametrically opposed sector 19 of relatively large mass, and, therefore, the amplitude of vibration in the radial direction at the outer end or periphery of each of the sectors 18 of relatively small mass is substantially greater than, or magnified with respect to the amplitude of the radially directed vibration at the outer edge or periphery of each sector 19 of relatively large mass. Further, since the sectors 18 and 19 are arranged alternately around each lamination 16 the net center of gravity of each lamination, and hence of the body 11 made up of a series of such laminations, remains at the central axis of the body 11, thereby to avoid gross vibrations or dynamic unbalance of the shaft 12 when rotated with the transducer body 11 thereon.

Since the desired radial vibrations of magnified amplitude occur at the outer ends of the sectors 18 of relatively small mass, the outer ends of the narrow stems constituting the major portion of the sectors 18 may be provided with circumferential enlargements, as at 29, so that the desired radial vibrations of magnified amplitude will be available over the substantial peripheral portions of the body 11 constituted by the arcuate outer edges of the circumferential enlargements 20. As is apparent in FIG. 2, each of the circumferential enlargements 2t) preferably tapers towards its opposite ends, thereby to avoid riexural vibrations thereof and to ensure that the radially directed vibrations will be of uniform magnified amplitude along the entire arcuate outer edge of each circumferential enlargement iii.

When the device It) is in the form of a rotatable transducer, as illustrated in the drawing, the biased, high frequency alternating current may be supplied to the energizing or exciting windings 15 through slip rings 21 (FIG. 1) carried by an insulating collar 22 on shaft 12 and being connected by suitable conductors 23 to the windings l5, and through stationary brushes 24 which engage the slip rings 21 and are connected, as by conductors 25, to a suitable conventional generator or other source of the necessary biased, high frequency alternating current, indicated diagrammatically at 31.

All of the laminations 16 making up the body 11 may be axially superposed, that is, arranged with their respec tive sectors 18 and 1% in axial alignment, in which case the peripheral surface of body 11 will exhibit circumferentially successive zones extending along the entire length of the body Ill and at which radial vibrations of relatively small and relatively large amplitude alternately occur. On the other hand, as illustrated in FIG. 1, the stack of laminations 16 making up the body 11 may be divided into axially segregated groups, generally indicated at A, B and C, with the laminations in each of said groups having their respective sectors 18 and 19 in axial alignment with each other, but with the sectors 18 of relatively small mass in the adjacent groups of laminations being angularly offset with respect to each other, for example, by the angular extent between the radial center lines of adjacent sectors 18 and 1% in each lamination 116, as illustrated in FIG. 1, or by any other desired angular extent. Thus, the portions or zones of the peripheral surface of body 11 corresponding to the outer edges of the sectors'18 of relatively small mass at which radial vibrations of magnified amplitude occur will not be axially aligned in all of the successive groups A, B and C of the laminations, but rather will be circumferentially staggered along the axial length of body 11.

When the successive groups of laminations A, B and C are circumferentially staggered, as described above, separators or spacers 26 may be inserted between the adjacent groups of laminations and provided with recessed faces to accommodate the energizing windings 15 provided for each of the groups of laminations.

Although the device It) in the form of a rotary transducer developing radial vibrations of magnified amplitude at zones of its peripheral surface has its energizing windings 15 associated only with the sectors 18 of relatively small mass, it is to be understood that the same desired results will be achieved, namely, the development of radial vibrations of magnified amplitude, when the energizing windings are associated with the sectors 19 of relatively large mass, or with both the sectors 18 and 19.

In the above described device It), the energizing Windings 15 are associated directly with the body 11 so that the device It functions as a transducer developing the desired radial vibrations directly within the body 11. However, it is to be understood that, in accordance with the present invention, longitudinal vibrations generated by a transducer may be first converted into radial vibrations which are then magnified in accordance with the principles described above. Thus, as shown by way of example in FIGS. 3 and 4, a device embodying the present invention, and there generally identified by the reference numeral Itla may include a body 11a made up of an axially arranged stack of laminations 16a which may have the same configuration as the previously described laminations 16, but need only be formed of a suitably high strength material having a high mechanical Q, for

example, Monel metal, but need not be formed of a magnetostrictive material. The laminations 16a forming the acoustic impedance transformer 11a are brazed, soldered or otherwise rigidly secured on a radial flange or enlargement 27 located at the nodal plane of longitudinal vibrations transmitted through a connecting body 28 from a magnetostrictive transducer which may consist of a stack of nickel or other magnetostrictive laminations 29 rigidly secured, at one end, to an end of connecting body 28, and extending loosely through a fixed insulatingcasing 30 carrying the energizing winding a to which biased, high frequency alternating current is supplied from a suitable generator or other source (not shown).

The mechanical vibrator consisting of the laminations 29 of the transducer and the connecting body 28 carrying the acoustic impedance transformer 11a may be rotatably mounted, at its opposite ends, in bearings 13a carried by a frame 14a so that the entire assembly may be rotated about the longitudinal axis of the mechanical vibrator.

The length of the laminations 29 of the transducer and the length of the connecting body 28 are selected with reference to the desired frequency of vibrations so as to be equal to an integral number of half wavelengths of the compressional waves introduced in the laminations by magneto-striction as a result of biased, alternating current delivered to the winding 15a at the desired high frequency, whereby the laminations 29 and the connecting body 28 are resonant at such high frequency and standing waves are set up therein with loops of longitudinal motion at the ends of the laminations and at the ends of the connecting body. The acoustic impedance transformer 11a is diametrically dimensioned so that it is also resonant at the frequency of the longitudinal vibrations or standing compressional waves transmitted to connecting body 28 from the lamination 29 of the transducer. Since the transformer 11a is located on the flange or enlargement 27 of connecting body 28 at a nodal point of the longitudinal vibrations in the latter, the periphery of the flange or radial enlargement 27 vibrates radially, and such radial vibrations are transmitted to the laminations 16a of transformer 11a.

The laminations 16a, being similar to the previously described laminations 16, are radially slotted, as at 17a, so that each lamination consists of sectors 18a and 19a arranged alternately around the lamination and having relatively small and relatively large masses, respectively, with each sector 18a of relatively small mass being diametrically opposed by a sector 19a of relatively large mass. Thus, as previously described in detail with reference to the embodiment of the invention illustrated in FIGS. 1 and 2, the amplitude of the radial vibrations transmitted to the transformer 11a from the connecting body 28 is magnified at the circumferential enlargements 20a forming the outer edges of the sectors 18a of relatively small mass.

Although the transformer 11a of FIG. 3 is shown as being made up of a stack of laminations 16a which are axially superposed, that is, having their respective sectors 18a and 19a in axial alignment, so that the peripheral zones at which the magnified amplitude of radial vibrations occurs extend axially along the entire length of the transformer 11a, it will be apparent that the laminations 16a of the transformer can be divided into groups having their sectors 18a of relatively small mass circumferentially staggered with respect to each other, thereby to circumferentially stagger the zones of magnified amplitude radial vibrations along the axial length of the acoustic impedance transformer, as in the arrangement of FIG. 1.

Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawing, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention, except as' defined in the appended claims.

What is claimed is: i 1. A device for magnifying the amplitude of radial vibrations comprising (A) vA generally circular body; and (B) Means for effecting radial vibration of said body at the fundamental mode of vibration of the latter; (C) Said body having diametrically opposed sectors of relatively small mass and relatively large mass, respectively, so that the average radial velocity in each sector of relatively small mass is substantially greater than the average radial velocity in the diametrically opposed sector of relatively large mass, thereby to provide radial vibrations of magnified amplitude at the peripheries of said sectors of relatively small mass. 2. A device for magnifying the amplitude of radial vibrations as in claim 1;

(a) wherein said body is formed of a magnetostrictivc material; and (b) wherein said means for elfecting radial vibration of the body includes energizing windings around at least certain of said sectors to generate radially directed compressional waves therein when biased alternating current is supplied to said windings at the resonant frequency of said body. 3. A device for magnifying the amplitude of radial vibrations as in claim 1;

(a) wherein said means for effecting radial vibration of the body includes (1) transducer means operative to generate longitudinal vibrations at a predetermined frequency, and (2) a connecting body coupled to said transducer means to receive said longitudinal vibrations from the latter and having a length equal to an integral number of half wavelengths of said longitudinal vibrations so that loops of longitudinal motion occur at the opposite ends of said connecting body and at least one nodal point occurs intermediate said opposite ends; and (12) wherein said generally circular body is mounted centrally on said connecting body at said nodal point and is diametrically dimensioned to resonate at said predetermined frequency. 4. A device for magnifying the amplitude of radial vibrations as in claim 1;

wherein said generally circular body includes an axially arranged stack of laminations each having diametrically opposed sector-shaped portions of relatively small mass and relatively large mass, respectively. 5. A device for magnifying the amplitude of radial vibrations as in claim 4;

wherein said laminations of the body are axially superposed throughout the axial length of said body so that the sector-shaped portions of relatively small mass of all of said laminations are in axial alignment with each other. 6. A device for magnifying the amplitude of radial vibrations as in claim 4;

wherein at least certain of said laminations have their sector-shaped portions of relatively small mass offset circumferentially with respect to the corresponding sector-shaped portions of the other laminations so that said body has peripheral zones of magnified radial vibrations which are circumferentially offset at successive axial locations along said body. 7. A device for magnifying the amplitude of radial vibrations as in claim 1;

wherein said body has odd numbers of said sectors of relatively small mass and of said sectors of relatively large mass, and said sectors of relatively small and large mass are alternately arranged around said body.

a 8. A device for magnifying the amplitude of radial peripheral extent at which the radial vibrations of vibrations a in clai 7; magnified amplitude are obtained.

wherein said body has generally radial slots between t device magnifying the amplitude of radial said alternately arranged sectors of relatively small i vlbratlolls g Qlalm 9; and large mass '5 wherein sa1d circumferential enlargement of each sector of relatively small mass tapers from said stem so as A device for magmfymg amplitude of radial to avoid flexural vibration of said enlargement.

vibrations as in claim 8;

wherein each of said sectors of relatively small mass References Cited in the file Of this Patent has a radial stem and a circumferential enlarge- 10 UN ED STATES PATENTS ment at its outer end defining a relatively large Re. 25,033 Balamuth et a1 Aug 29 1961 

1. A DEVICE FOR MAGNIFYING THE AMPLITUDE OF RADIAL VIBRATIONS COMPRISING (A) A GENERALLY CIRCULAR BODY; AND (B) MEANS FOR EFFECTING RADIAL VIBRATION OF SAID BODY AT THE FUNDAMENTAL MODE OF VIBRATION OF THE LATTER; (C) SAID BODY HAVING DIAMETRICALLY OPPOSED SECTORS OF RELATIVELY SMALL MASS AND RELATIVELY LARGE MASS, RESPECTIVELY, SO THAT THE AVERAGE RADIAL VELOCITY IN EACH SECTOR OF RELATIVELY SMALL MASS IS SUBSTANTIALLY GREATER THAN THE AVERAGE RADIAL VELOCITY IN THE DIAMETRICALLY OPPOSED SECTOR OF RELATIVELY LARGE MASS, THEREBY TO PROVIDE RADIAL VIBRATIONS OF MAGNIFIED AMPLITUDE AT THE PERIPHERIES OF SAID SECTORS OF RELATIVELY SMALL MASS. 